The Correlation between Polybrominated Diphenyl Ethers (PBDEs) and Thyroid Hormones in the General Population: A Meta-Analysis

ObjectiveCertain epidemiological studies have suggested exposure to polybrominated diphenyl ethers (PBDEs) affect the production and secretion of thyroid hormones (TH); however, conflicting results have been reported in different studies. There is not a convincing conclusion about this debate to date.ConclusionThe findings in our meta-analysis indicate the effects of PBDEs on thyroid function may mainly depend on PBDEs exposure and their levels found in serum. The relationship between PBDEs exposure and changes in thyroid function seem to fit an approximate u-shaped curve. These predictions await further verification, namely a prospective longitudinal study.     

Substance Flow Analysis of Wastes Containing Polybrominated Diphenyl Ethers

The present article examines flows and stocks of Stockholm Convention regulated pollutants, commercial penta‐ and octabrominated diphenyl ether (cPentaBDE, cOctaBDE), on a city level. The goals are to (1) identify sources, pathways, and sinks of these compounds in the city of Vienna, (2) determine the fractions that reach final sinks, and (3) develop recommendations for waste management to ensure their minimum recycling and maximum transfer to appropriate final sinks. By means of substance flow analysis (SFA) and scenario analysis, it was found that the key flows of cPentaBDE stem from construction materials. Therefore, end‐of‐life (EOL) plastic materials used for construction must be separated and properly treated, for example, in a state‐of‐the‐art municipal solid waste (MSW) incinerator. In the case of cOctaBDE, the main flows are waste electrical and electronic equipment (WEEE) and, possibly, vehicles. Most EOL vehicles are exported from Vienna and pose a continental, rather than a local, problem. According to the modeling, approximately 73% of cOctaBDE reached the final sink MSW incinerator, and 17% returned back to consumption by recycling. Secondary plastics, made from WEEE, may thus contain significant amounts of cOctaBDE; however, uncertainties are high. According to uncertainty analysis, the major cause is the lack of reliable values regarding cOctaBDE concentrations in European WEEE categories 3 and 4, including cathode ray tube monitors for computers and televisions. We recommend establishing a new, goal‐oriented data set by additional analyses of waste constituents and plastic recycling samples, as well as establishing reliable mass balances of polybrominated diphenyl ethers’ flows and stocks by means of SFA.     

Reductive Debromination of Polybrominated Diphenyl Ethers by Anaerobic Bacteria from Soils and Sediments

Polybrominated diphenyl ethers (PBDEs) have attracted attention recently due to their proven adverse effects on animals and their increasing concentrations in various environmental media and biota. To gain insight into the fate of PBDEs, microcosms established with soils and sediments from 28 locations were investigated to determine their debromination potential with an octa-brominated diphenyl ether (octa-BDE) mixture consisting of hexa- to nona-BDEs. Debromination occurred in microcosms containing samples from 20 of the 28 locations when they were spiked with octa-BDE dissolved in the solvent trichloroethene (TCE), which is a potential cosubstrate for stimulating PBDE debromination, and in microcosms containing samples from 11 of the 28 locations when they were spiked with octa-BDE dissolved in nonane. Debromination products ranging from hexa- to mono-BDEs were generated within 2 months. Notably, the toxic tetra-BDEs accounted for 50% of the total product. In sediment-free culture C-N-7* amended with the octa-BDE mixture and nonane (containing 45 nM nona-BDE, 181 nM octa-BDEs, 294 nM hepta-BDE, and 19 nM hexa-BDE) there was extensive debromination of the parent compounds, which produced hexa-BDE (56 nM), penta-BDEs (124 nM), and tetra-BDEs (150 nM) within 42 days, possibly by a metabolic process. A 16S rRNA gene-based analysis revealed that Dehalococcoides species were present in 11 of 14 active microcosms. However, unknown debrominating species in some of the microcosms debrominated the octa-BDE mixture in the absence of other added halogenated electron acceptors (such as TCE). These findings provide information that is useful for assessing microbial reductive debromination of higher brominated PBDEs to less-brominated congeners, a possible source of the more toxic congeners (e.g., penta- and tetra-BDEs) detected in the environment.Since they were first developed in the 1960s, polybrominated diphenyl ethers (PBDEs) have been used as flame retardant additives in an array of common household and industrial appliances. As a result of their widespread use, PBDEs have become ubiquitous environmental contaminants, and increasing levels have been detected in the air, soil, and water (5, 12). In a recent study, Leung et al. reported the highest PBDE concentrations in soil samples (2.7 to ∼4.3 ppb) and combusted residues (33.0 to ∼97.4 ppb) that were collected in Guiyu, Guangdong Province, China (18). More worrisome is the fact that increasing concentrations of PBDEs have also been detected in marine mammals, birds, fishes, and human tissues (3, 14, 20, 30), and 63 ppm of PBDEs in bird eggs is the highest level ever found in biota (23). The PBDE concentrations in both environmental samples and biota have been increasing exponentially, with a doubling time of 4 to 6 years (5, 12). Although the PBDEs comprise 209 different congeners designated 1 to 209, the PBDE congeners most often detected in biota (e.g., human tissues) include tetra-brominated diphenyl ether (tetra-BDE) (congener 47), penta-BDEs (congeners 99 and 100), and hexa-BDEs (congeners 153 and 154), which may have originated directly from a commercially available penta-BDE technical mixture or indirectly via breakdown of an octa- or deca-BDE technical mixture (10, 12). PBDEs began to receive worldwide scientific and public attention when a temporal study performed from 1972 to 1997 revealed increasing concentrations of PBDEs in Swedish human breast milk (19). Toxicological studies of rodents using a commercial penta-BDE mixture (including tetra-, penta- and hexa-BDEs) and congeners in a commercial octa-BDE mixture (such as hepta-BDE [congener 183] and octa-BDE [congener 203]) revealed developmental neurotoxicity, reproductive toxicity, liver toxicity, and disruption of thyroid hormone levels (24, 26, 29).To date, studies of PBDEs have focused mainly on detection of these compounds in the environment and their potential adverse health effects; only a few studies have reported microbial debromination of PBDEs (7, 10, 22, 25). Recently, He et al. demonstrated debromination of a technical octa-BDE mixture by pure isolates of Dehalococcoides species, which generated hepta- to di-BDEs after 6 months of incubation (10). Additionally, microbes belonging to the genera Dehalobacter and Desulfitobacterium were also found to be able to debrominate individual PBDE congeners present in commercial octa-BDE mixtures (10, 22). However, the debromination of PBDEs in both studies required the presence of a primary electron acceptor (e.g., chloroethenes or chlorophenols); in other words, debromination occurred cometabolically.In addition to debromination of PBDEs by pure cultures, a previous study demonstrated that in anaerobic sludge 5% of added deca-BDE (congener 209) was debrominated to nona- and octa-BDEs (total amount of product, 0.5 nmol) after 238 days of incubation (7). Moreover, another study showed that deca-BDE was debrominated to products ranging from nona-BDEs to hexa-BDEs in 3.5 years with anaerobic sediments as the inocula (25). These findings suggest that microbial reductive debromination of highly brominated congeners, such as deca-, nona-, octa-, and hepta-BDEs, may contribute to formation of less-brominated PBDEs in the environment, which are potentially more toxic (e.g., tetra- and penta-BDEs). Additionally, debromination of less-brominated PBDE congeners, such as di-BDE, to mono-BDE and diphenyl ether was demonstrated in a fixed-film plug flow biological reactor (21). Besides microbial debromination, highly brominated PBDEs were also found to be transformed to lower congeners via photodegradation or in vivo metabolism in aquatic and terrestrial animals (1, 16).This study was initiated to obtain information about the distribution of microorganisms capable of debrominating highly brominated PBDE congeners to more toxic daughter products or the final product diphenyl ether by assessing microcosm samples collected from various locations. Debromination of an octa-BDE mixture was evaluated in the presence of the potential energy-generating cosubstrate trichloroethene (TCE) (PBDEs dissolved in TCE) or in the presence of the relatively inert solvent nonane (PBDEs dissolved in nonane). The latter experiment provided, for the first time, information about the possible microbes living on the energy generated from the debromination of an octa-BDE mixture in the absence of any cosubstrate, such as TCE or another primer compound. Initial insights into the key debrominating microbes were obtained by using genus-specific 16S rRNA gene-based techniques.     

Polybrominated Diphenyl Ethers (PBDEs) in Marine Fish and Dietary Exposure in Newfoundland

EcoHealth - Presence of PBDEs tested in 127 liver samples from Atlantic Cod (Gadus morhua) and Turbot (Scophthalmus Maximus) and 80 adult participants from two rural Newfoundland communities....     

Quantification of Hydroxylated Polybrominated Diphenyl Ethers (OH-BDEs), Triclosan,and Related Compounds in Freshwater and Coastal Systems

Hydroxylated polybrominated diphenyl ethers (OH-BDEs) are a new class of contaminants of emerging concern, but the relative roles of natural and anthropogenic sources remain uncertain. Polybrominated diphenyl ethers (PBDEs) are used as brominated flame retardants, and they are a potential source of OH-BDEs via oxidative transformations. OH-BDEs are also natural products in marine systems. In this study, OH-BDEs were measured in water and sediment of freshwater and coastal systems along with the anthropogenic wastewater-marker compound triclosan and its photoproduct dioxin, 2,8-dichlorodibenzo-p-dioxin. The 6-OH-BDE 47 congener and its brominated dioxin (1,3,7-tribromodibenzo-p-dioxin) photoproduct were the only OH-BDE and brominated dioxin detected in surface sediments from San Francisco Bay, the anthropogenically impacted coastal site, where levels increased along a north-south gradient. Triclosan, 6-OH-BDE 47, 6-OH-BDE 90, 6-OH-BDE 99, and (only once) 6’-OH-BDE 100 were detected in two sediment cores from San Francisco Bay. The occurrence of 6-OH-BDE 47 and 1,3,7-tribromodibenzo-p-dioxin sediments in Point Reyes National Seashore, a marine system with limited anthropogenic impact, was generally lower than in San Francisco Bay surface sediments. OH-BDEs were not detected in freshwater lakes. The spatial and temporal trends of triclosan, 2,8-dichlorodibenzo-p-dioxin, OH-BDEs, and brominated dioxins observed in this study suggest that the dominant source of OH-BDEs in these systems is likely natural production, but their occurrence may be enhanced in San Francisco Bay by anthropogenic activities.     

Polybrominated Diphenyl Ethers (PBDEs) in PM2.5, PM10, TSP and Gas Phase in Office Environment in Shanghai,China: Occurrence and Human Exposure

To evaluate risk via inhalation exposure of polybrominated diphenyl ethers (PBDEs) in office environment, thirty-six pairs air samples including PM_2.5 (particles with aerodynamic diameter less than 2.5 μm), PM₁₀ (particles with aerodynamic diameter less than 10 μm), total suspended particles (TSP) with matching gas phase were collected in office environment in Shanghai, China. The average concentrations of PM_2.5, PM₁₀ and TSP were 20.4, 27.2 and 50.3 μg/m₃, respectively. Σ₁₅PBDEs mean concentrations in PM_2.5, PM₁₀, TSP and gas phase were 51.8, 110.7, 148 and 59.6 pg/m³, respectively. Much more PBDEs distributed in fine fractions than coarse ones. PBDEs congener profiles found in PM_2.5, PM₁₀ and TSP (dominated by BDE-209) were different from that in gas phase (dominated by the tri- to penta-BDEs). Approximately 3.20 pg/kg/d PM_2.5 bound PBDEs can be inhaled into the lung; 3.62 pg/kg/d PM₁₀-PM_2.5(particles with aerodynamic diameter of 2.5-10 μm) bound PBDEs tended to be deposited in the upper part of respiratory system, and the intake of PBDEs via gas-phase was 2.74 pg/kg/d. The exposure of PBDEs was far below the minimal risk levels (MRLs), indicating lower risk from PBDEs via inhalation in the studied office in Shanghai.     

Induction of Adipocyte Differentiation by Polybrominated Diphenyl Ethers (PBDEs) in 3T3-L1 Cells

Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants that were extensively used in commercial products. PBDEs are ubiquitous environmental contaminants that are both lipophilic and bioaccumulative. Effects of PBDEs on adipogenesis were studied in the 3T3-L1 preadipocyte cell model in the presence and absence of a known adipogenic agent, dexamethasone (DEX). A PBDE mixture designed to mimic body burden of North Americans was tested, in addition to the technical mixture DE-71 and the individual congener BDE-47. The mixture, DE-71, and BDE-47 all induced adipocyte differentiation as assessed by markers for terminal differentiation [fatty acid binding protein 4 (aP2) and perilipin] and lipid accumulation. Characterization of the differentiation process in response to PBDEs indicated that adipogenesis induced by a minimally effective dose of DEX was enhanced by these PBDEs. Moreover, C/EBPα, PPARγ, and LXRα were induced late in the differentiation process. Taken together, these data indicate that adipocyte differentiation is induced by PBDEs; they act in the absence of glucocorticoid and enhance glucocorticoid-mediated adipogenesis.     

甲状腺功能减退患者血清甲状腺激素、同型半胱氨酸及血脂水平测定的临床意义

目的:探讨甲状腺功能减退患者血清同型半胱氨酸(Hcy)、甲状腺激素(TH)及血脂水平测定的临床意义。方法:选取2016年2月-2017年2月期间我院收治的甲状腺功能减退患者101例为观察组,选取同期于我院体检的健康志愿者80例为对照组。检测所有研究对象甲状腺素(FT4)和三碘甲状腺原氨酸(FT3)、Hcy及血脂[甘油三酯(TG)、总胆固醇(TC)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)]变化水平。比较观察组治疗前后、对照组与观察组治疗前FT3、FT4、Hcy及血脂水平,采用Pearson相关性分析血清Hcy与FT3、FT4、血脂水平的相关性。结果:观察组患者治疗后FT3、FT4均较治疗前升高,Hcy、TC、LDL-C均较治疗前降低(P0.05),而观察组患者治疗前后TG、HDL-C比较差异无统计学意义(P0.05)。观察组治疗前FT3、FT4、HDL-C水平明显低于对照组,而Hcy、TG、TC、LDL-C则明显高于对照组(P0.05)。经Pearson相关性分析显示,甲状腺功能减退患者Hcy与FT3、FT4呈负相关(P0.05),与TC、TG呈正相关(P0.05),而与LDL-C、HDL-C无相关性(P0.05)。结论:甲状腺功能减退患者的FT3、FT4、Hcy及血脂水平表达异常,且Hcy与FT3、FT4、血脂水平密切相关,临床上可通过监测甲状腺功能减退患者的上述指标,有助于评估患者的病情程度。     

Blood Lead Levels and Associated Factors among Children in Guiyu of China: A Population-Based Study

Objectives

Children''s health problems caused by the electronic waste (e-waste) lead exposure in China remains. To assess children''s blood lead levels (BLLs) in Guiyu of China and investigate risk factors of children''s elevated BLLs in Guiyu.

Material and Methods

842 children under 11 years of age from Guiyu and Haojiang were enrolled in this population-based study during 2011–2013. Participants completed a lifestyle and residential environment questionnaire and their physical growth indices were measured, and blood samples taken. Blood samples were tested to assess BLLs. Children''s BLLs between the two groups were compared and factors associated with elevated BLLs among Guiyu children were analyzed by group Lasso logistic regression model.

Results

Children living in Guiyu had significant higher BLLs (7.06 µg/dL) than the quantity (5.89 µg/dL) of Haojiang children (P<0.05). Subgroup analyses of BLLs exceeding 10 µg/dL showed the proportion (24.80%) of high-level BLLs for Guiyu children was greater than that (12.84%) in Haojiang (P<0.05). Boys had greater BLLs than girls, irrespectively of areas (P<0.05). The number of e-waste piles or recycling workshops around the house (odds ratio, 2.28; 95% confidence interval [CI], 1.37 to 3.87) significantly contributed to the elevated BLLs of children in Guiyu, and girls had less risk (odds ratio, 0.51; 95% CI, 0.31 to 0.83) of e-waste lead exposure than boys.

Conclusions

This analysis reinforces the importance of shifting e-waste recycling piles or workshops to non-populated areas as part of a comprehensive response to e-waste lead exposure control in Guiyu. To correct the problem of lead poisoning in children in Guiyu should be a long-term mission.     

Fluoride Toxicity and Status of Serum Thyroid Hormones, Brain Histopathology, and Learning Memory in Rats: A Multigenerational Assessment

High-fluoride (100 and 200?ppm) water was administered to rats orally to study the fluoride-induced changes on the thyroid hormone status, the histopathology of discrete brain regions, the acetylcholine esterase activity, and the learning and memory abilities in multigeneration rats. Significant decrease in the serum-free thyroxine (FT4) and free triiodothyronine (FT3) levels and decrease in acetylcholine esterase activity in fluoride-treated group were observed. Presence of eosinophilic Purkinje cells, degenerating neurons, decreased granular cells, and vacuolations were noted in discrete brain regions of the fluoride-treated group. In the T-maze experiments, the fluoride-treated group showed poor acquisition and retention and higher latency when compared with the control. The alterations were more profound in the third generation when compared with the first- and second-generation fluoride-treated group. Changes in the thyroid hormone levels in the present study might have imbalanced the oxidant/antioxidant system, which further led to a reduction in learning memory ability. Hence, presence of generational or cumulative effects of fluoride on the development of the offspring when it is ingested continuously through multiple generations is evident from the present study.     

Plasma Zinc,Copper, and Serum Thyroid Hormones and Insulin Levels After Zinc Supplementation Followed by Placebo in Competitive Athletes

Intense physical activity is associated with biological adaptations involving hormones and trace elements. Zinc supplementation may affect plasma copper concentration, thyroid-stimulating hormone (TSH), thyroid hormones, insulin, and glucose homeostasis, but data in athletes are scarce. The aim of this study was to evaluate in competitive athletes (cyclists, n = 7, 32 ± 8 years) the effect of zinc supplementation (22 mg/day as zinc gluconate) during 30 days, and discontinuation using placebo (maltodextrin) during the following 30 days, on plasma zinc and copper concentrations, serum thyroid hormones, insulin and glucose levels, and HOMA2-IR. Compared to baseline, plasma zinc and Zn:Cu plasma ratio increased, but plasma copper decreased after zinc supplementation (day 30) and discontinuation (day 60) (p < 0.05). Zn supplementation and discontinuation had no effect on TSH, T3, and T4. Fasting serum insulin and HOMA2-IR increased (27% and 47%, respectively) on day 60 compared to baseline (p = 0.03), suggesting a delayed effect of zinc supplementation. Moreover, plasma zinc was positively associated with serum insulin (r = 0.87, p = 0.009) and HOMA2-IR (r = 0.81, p = 0.03) after zinc supplementation (day 30), indicating that supplemental zinc may impair glucose utilization in cyclists.     

桥本氏病合并甲状腺乳头状癌患者血清甲状腺相关激素水平的变化及意义

目的:探究桥本氏病(HT)合并甲状腺乳头状癌(PTC)患者血清甲状腺相关激素水平的变化及意义。方法:对我院148例HT患者的临床资料进行回顾性分析,根据其是否合并PTC分为HT合并PTC组(n=68)和单纯HT组(n=80)。比较两组患者性别、年龄及血清促甲状腺激素(TSH)、甲状腺功能指标[游离三碘甲腺原氨酸(FT3)、游离甲状腺素(FT4)]、抗甲状腺抗体[甲状腺球蛋白抗体(TGAb)、甲状腺过氧物酶抗体(TPOAb)]水平等临床资料差异,分析血清TSH水平变化及意义。结果:HT合并PTC组患者男性比例、年龄、病程及血清TSH水平均大于单纯HT组,血清TGAb、TPOAb水平则均小于单纯HT组(P0.05);血清FT3、FT4水平比较差异无统计学意义(P0.05)。HT合并PTC患者组血清TSH4.2 m IU/L患者占比高于血清TSH正常组(P0.05)。血清TSH4.2 m IU/L患者中HT合并PTC患者的占比大于血清TSH水平正常的患者(P0.05)。HT合并PTC患者中,血清TSH水平4.2 m IU/L患者中央区淋巴结转移发生率高于血清TSH水平正常患者(P0.05);血清TSH4.2 m IU/L与血清TSH正常患者多灶癌发生率比较差异无统计学意义(P0.05)。结论:HT患者血清TSH水平升高可能促进其甲状腺组织癌变,HT合并PTC患者血清TSH水平升高可能促进其中央区淋巴结转移。     

Effects of Dietary Iodine and Selenium on Nutrient Digestibility,Serum Thyroid Hormones,and Antioxidant Status of Liaoning Cashmere Goats

Forty-eight 2-year-old Liaoning Cashmere goats (body weight = 38.0 ± 2.94 kg) were used to investigate the effects of dietary iodine (I) and selenium (Se) supplementation on nutrient digestibility, serum thyroid hormones, and antioxidant status during the cashmere telogen period to learn more about the effects of dietary I and Se on nutrition or health status of Cashmere goats. The goats were equally divided into six groups of eight animals each that were treated with 0, 2, or 4 mg of supplemental I/kg dry matter (DM) and 0 or 1 mg of supplemental Se/kg DM in a 2 × 3 factorial arrangement of treatments. The six treatments were I₀Se₀, I₂Se₀, I₄Se₀, I₀Se₁, I₂Se₁, and I₄Se₁. The concentrations of I and Se in the basal diet were 0.67 and 0.09 mg/kg DM, respectively. The study started in March and proceeded for 45 days. Supplemental I or Se alone had no effect on nutrient digestibility and nitrogen metabolism. However, the interaction between I and Se was significant regarding the digestibility of acid detergent fiber (ADF; P < 0.05), and compared with group I₄Se₁, the digestibility of ADF was significantly increased in group I₄Se₀ (P < 0.05). Selenium supplementation did not affect serum triiodothyronine (T₃) or thyroxine (T₄) concentrations. However, the concentration of serum T₄ but not that of T₃ was significantly increased with I supplementation (P < 0.05). In addition, serum superoxide dismutase (SOD) activity was not affected (P > 0.05), but serum glutathione peroxidase (GSH-Px) activity was significantly decreased by I supplementation (P < 0.05). The antioxidant status was improved by Se supplementation, and the activities of SOD and GSH-Px were significantly increased (P < 0.05).     

Persistent or Recurrent Disease in Thyroid Cancer Survivors Who Have Elevated Serum Antithyroglobulin Antibodies

ObjectiveDetection of residual differentiated thyroid cancer is important but difficult. A variety of imaging modalities and biochemical markers has been used with moderately good success. We hypothesized that elevated perioperative serum antithyroglobulin antibody (TgAb) levels would also be a predictive marker for persistent or recurrent thyroid cancer.MethodsWe performed a retrospective analysis of 277 differentiated thyroid cancer survivors divided into 2 groups: (1) those with low or normal serum TgAb (TgAb−) and (2) those with elevated serum TgAb (TgAb+). All patients were seen at one major academic medical center. Patients were followed for a median of 7.54 years.ResultsPatients in the TgAb+ group were more likely to have positive lymph nodes at initial surgery, to be assigned to a higher American Joint Committee on Cancer stage, and to have significantly higher incidence of persistent/recurrent disease. The higher incidence of persistent/recurrent cancer was significant under univariable and multivariable (including TgAb status, age, and sex) Cox proportional hazards model analysis.ConclusionWe conclude that individuals with elevated serum TgAb at the outset should be followed with a higher index of suspicion for persistent/recurrent thyroid cancer.     

Relationships between Thyroid Hormones, Blood Rheology, and Lipid Profile in Athletes

The interrelation of thyroid hormones with blood rheology and lipid profile was studied in athletes (N = 12). A decrease in blood viscosity in the athletes was caused by a lower erythrocyte rigidity index, which correlated with an increased reticulocyte count (P = 0.022), a decreased mean concentration of hemoglobin per cell (MCHC) (P = 0.006), and an increased level of thyrotropin (TTH) (P = 0.040). By multiple regression analysis, MCHC was found to be the primary correlate of the erythrocyte rigidity index (P = 0.044). The interrelation of TTH with the rigidity index was explained by a positive correlation of TTH with the reticulocyte count (P = 0.022). The level of triiodothyronine (T₃) was similar in the athletes and the control subjects and negatively correlated with total cholesterol (Ch) (P = 0.033) and low-density lipoprotein cholesterol (LDL Ch) (P = 0.048), which both correlated positively with blood and plasma viscosity and erythrocyte aggregation (P < 0.05 or 0.01). Thus, the decrease in LDL Ch in the athletes, which was closely related with the higher blood and plasma fluidities and with erythrocyte aggregation, was at least partly due to the effect of T₃.     

Photolysis of Low-Brominated Diphenyl Ethers and Their Reactive Oxygen Species-Related Reaction Mechanisms in an Aqueous System

To date, no report was concerned with participation of reactive oxygen species in waters during photolysis of low-brominated diphenyl ethers (LBDEs). Herein, we found that electron spin resonance (ESR) signals rapidly increased with increasing irradiation time in the solution of LBDEs and 4-oxo-TMP solutions. But this phenomenon did not occur in the presence of NaN₃ (¹O₂ quencher) demonstrating generation of ¹O₂ in process of LBDEs photolysis. The indirect photolytic contribution rate for BDE-47 and BDE-28 was 18.8% and 17.3% via ¹O₂, and 4.9% and 6.6% via ·OH, respectively. Both D₂O and NaN₃ experiments proved that the indirect photolysis of LBDEs was primarily attributable to ¹O₂. The bimolecular reaction rate constants of ¹O₂ with BDE-47 and BDE-28 were 3.12 and 3.64 × 10⁶ M^-1 s^-1, respectively. The rate constants for BDE-47 and BDE-28 (9.01 and 17.52 × 10⁻³ min^-1), added to isopropyl alcohol, were very close to those (9.65 and 18.42 × 10⁻³ min^-1) in water, proving the less indirect photolytic contribution of ·OH in water. This is the first comprehensive investigation examining the indirect photolysis of LBDEs in aqueous solution.